1. Field of the Invention
This invention relates to a battery having an identification with which to identify the battery. More specifically, this invention relates to an apparatus and a method of managing and displaying the remaining battery power correctly.
2. Description of the Related Art
Electronic apparatus, such as personal computers or TV cameras, have become increasingly used as portable devices. Most such electronic apparatus use rechargeable batteries, including nickel cadmium storage and nickel metal hydride storage batteries.
The discharge characteristics of those batteries are shown in FIG. 33. While terminal voltage remains constant after a battery is used for a long time, it rapidly drops once the remaining battery power becomes low. Thus, terminal voltage of an electronic apparatus using this type of battery must be monitored. An alarm is output when the terminal voltage drops low (Time T1 in FIG. 33). If the electronic apparatus is still used, the operation stops at time T2.
Nickel metal hydride or nickel cadmium storage batteries have a disadvantage in that the electronic apparatus stops a short time after the alarm is output, thereby requiring users to carry new batteries or a charger with them.
A conventional charger is explained below using FIG. 34. FIG. 34 shows a charger for an exchangeable charging battery pack, indicated in the Japan Unexamined Patent Publication 2-294231. This charger has the following components. A code reader 96a reads an identification code 92a displayed on a battery pack 92 in which a exchangeable battery is stored. A memory unit 96c stores charge management data of the battery pack, including the number of charges, and the content of the identification code. A data processor 96b manages the battery pack, including the processing for determining whether the number of charges has reached a predetermined number of times based on the charge management data. A display unit 94 displays the battery information, including the results of processing done by the data processor.
Conventional electronic apparatus have problems. Alarms output suddenly, while an electronic apparatus is being used and the apparatus is stopped shortly. This is because the remaining battery power is detected by measuring the terminal voltage of the battery. There are chargers that manage batteries by attaching an identifier to each battery. It is a charger, however, that manages batteries with identifiers and not an electronic apparatus that manages batteries with the identifiers. Electronic apparatus itself does not manage charge information for each battery even when the battery has an identifier.